advertisement

SCIENCE SKILLS 2.3 Chapter Two: Science Skills 2.1 Mass and Volume 2.2 Density 2.3 Graphing 2.4 Solving Problems Section 2.3 Learning Goals Use graphs to create a visual representation of data. Analyze trends on a graph. Explain the difference between a direct relationship and an inverse relationship. Investigation 2C Thickness of Aluminum Foil Key Question: What is the thickness of aluminum foil? 2.3 Graphing A graph is a visual way to organize data. A scatterplot or XY graph is used to see if two variables are related. 2.3 Graphing A bar graph compares data grouped by a name or category. 2.3 Graphing A pie graph shows the amount each part makes of up of the whole (100%). 2.3 Graphing A “connect-the-dots” line graph is often used to show trends in data over time. 2.3 How to make an XY graph Scatterplots show how a change in one variable influences another variable. The independent variable is the variable you believe might influence another variable. The dependent variable is the variable that you hope will change as a result of the experiment. 2.3 How to make an XY graph Pressure is critical to safe diving. How does an increase in depth affect the pressure? What sort of graph would best show the relationship between pressure and depth? 2.3 How to make an XY graph 1. Choose x and y-axis Depth is the independent variable = x axis Pressure is the dependent variable = y axis 2. Make a scale Most graphs use ones, twos, fives or tens OR calculate the value per box 3. Plot your data 4. Create a title * Exception- when time is a variable 2.3 Identifying graph relationships In a direct relationship, when one variable increases, so does the other. The speed and distance variables show a direct relationship. 2.3 Identifying graph relationships When there is no relationship the graph looks like a collection of dots. No pattern appears. 2.3 Identifying graph relationships In an inverse relationship, when one variable increases, the other decreases. 2.3 Reading a graph What is the speed of the car at 50 cm? 1. Find the known value on the x axis Position = 50 cm 2. Draw a line vertically upward from 50 cm until it hits the curve. 3. Draw a line across horizontally to the yaxis from the same place on the curve. 4. Read the speed using the y axis scale. Speed = 76 cm/s